CASE 17393 Published on 18.08.2021

Unilateral axillary lymphadenopathies after COVID-19 vaccination: A diagnostic dilemma in breast imaging


Breast imaging

Case Type

Clinical Cases


Dr Nick Janssen, Dr Aljosja De Schepper, Dr Filip Deckers

GZA Sint-Augustinus, Antwerp, Belgium

University of Antwerp, Antwerp, Belgium


51 years, female; 39 years, female; 73 years, female

Area of Interest Breast, Lymph nodes ; Imaging Technique Mammography, Ultrasound, Ultrasound-Colour Doppler
Clinical History

We present a case series of three different patients who were referred to our radiology department for a mammography and ultrasound investigation.

1. A 51-year-old woman was referred by her general practitioner for pain in the left breast. No other important medical history was noted.

2. A 39-year-old woman referred by her gynaecologist for screening because of familial history of breast cancer at young age.

3. A 73-year-old woman came for annual check-up after left-sided breast cancer 10 years ago.

Imaging Findings

All three patients underwent conventional mammography using a full-field digital mammography system with 3D-tomosynthesis images and an additional ultrasound investigation.

Patient 1: Mammography revealed lymph nodes in both axillae (fig. 1a & b). Ultrasound showed a lymph node with thickened cortex and preserved fatty hilum in the left axilla (fig. 2b).

Patient 2: Mammography revealed asymmetrical presentation of multiple slightly enlarged lymph nodes in the left axilla (fig. 3b), which were confirmed on ultrasound (fig. 4a).

Patient 3: Mammography revealed post-operative changes in the left breast without tumour recurrence (fig. 5b) and an enlarged lymph node in the contralateral right axilla (fig. 5a). Ultrasound confirmed these findings and revealed the enlarged lymph node with thickened cortex, fatty hilum (fig. 6a) and increased vascularity on Doppler investigation (fig. 6b).

All three patients presented with unilateral axillary lymphadenopathies without other significant abnormalities in the breasts. Thorough anamnesis revealed that all these patients received a recent vaccine for COVID-19 in the ipsilateral upper arm. Normalization of these lymph nodes was seen after six weeks in all cases (fig. 2c, fig. 4b, fig. 6c).



In late 2019, a new virus emerged from the Hubei province in China causing a pandemic. The virus, later named COVID-19, was responsible for widespread morbidity, economic damage and social impact. [1–3] Many researchers and pharmaceutical companies invested with high priority in developing a potent and safe vaccine to contain this pandemic. Pfizer-BioNTech and Moderna were the first to receive FDA approval to start vaccinating the general population. These vaccines currently exist of two separate injections.

As with other vaccinations, some adverse effects are noted with the COVID-19 vaccination, ranging from local reactions at the injection site to systemic reactions, for example, fatigue or fever. Axillary swelling, tenderness and palpable lymph nodes are commonly reported after the first or second injection in both Pfizer-BioNTech and Moderna vaccines. [4, 5]

Clinical Perspective

As vaccine rates increases, more and more patients will present with unilateral axillary lymphadenopathies on the ipsilateral side of vaccination. This understanding presents itself with new diagnostic dilemmas to be taken into account in breast imaging, especially regarding screening and follow-up with history of malignancy. As axillary lymphadenopathies used to raise medical concern or suspicion of cancer recurrence, we currently have to consider the possibility of vaccine-induced reactive lymph nodes. [6–11]

Imaging Perspective

Enlarged lymph nodes after recent COVID-19 vaccination can be encountered on multiple modalities and have been reported on conventional mammography, ultrasound, MRI, CT as well as PET-CT. The presentation of these lymph nodes varies in the known literature, ranging from modest enlargement to big round-shaped lymph nodes with thickened hypervascular cortex and no visible hilum. They are usually ipsilateral to the injection site and are mostly found in the axilla. Other reports also mention enlarged lymph nodes in the infra- and supraclavicular region. As of our knowledge, the lymph nodes can persist for up to four or five weeks and potentially longer. [6–8]


With these new insights, it is necessary to suggest new guidelines and management strategies, especially in the setting of screening and in the follow-up of high-risk oncology patients. The Society of Breast Imaging already proposed guidelines addressing these problems, which can be found on their official site. [9–11]

Take-Home Message

With the reports of unilateral axillary lymphadenopathies after COVID-19 vaccination, breast imaging faces new diagnostic dilemmas which require new guidelines and management. Radiologists as well as clinicians and even patients need to be aware of this phenomenon in order to avoid unnecessary anxiety and to guarantee continuity of good care. Especially in patients with history of breast cancer who present with enlarged axillary lymph nodes, a recent vaccination has to be considered and correlated with clinical information. Follow-up in such cases should be suggested.  


Informed consent for publication has been obtained.

Differential Diagnosis List
COVID-19 vaccine-induced unilateral axillary lymphadenopathies
Other regional infections
Metastasis from breast
Non-breast malignancy
Silicone induced granulomatous adenitis
Final Diagnosis
COVID-19 vaccine-induced unilateral axillary lymphadenopathies
Case information
DOI: 10.35100/eurorad/case.17393
ISSN: 1563-4086